VDR and vitamin D deficiency: Significantly, our investigation revealed a notable association between vitamin D deficiency and the VDR Fok-I variant, particularly in relation to the T (f) allele, suggesting a potential genotype-phenotype interaction in the context of multiple sclerosis susceptibility (P = 0.03). This finding is consistent with a study by researchers [31], which also observed an increased risk of MS among individuals carrying the Fok-I polymorphism combined with low vitamin D intake.